Method of sequestering carbon dioxide

ABSTRACT

A method of sequestering carbon dioxide (CO 2 ) in an ocean comprises testing an area of the surface of a deep open ocean in order to determine the nutrients that are missing, applying to the area a first fertilizer that comprises an iron chelate, and measuring the amount of carbon dioxide that has been sequestered. The method may further comprise applying additional fertilizers, and reporting the amount of carbon dioxide sequestered. The method preferably includes applying a fertilizer in pulses. Each fertilizer releases each nutrient over time in the photic zone and in a form that does not precipitate.

BACKGROUND OF THE INVENTION

The field of the invention is controlling the amount of carbon dioxide(CO₂) in the atmosphere. This may have a significant effect on globalclimate change, including global warming.

The carbon dioxide content of the atmosphere has been increasing. Thisis based on measurements over the last 40 years or more. There isconcern that this increase may result in global climate change, whichover time may have an adverse effect on weather, sea level and humansurvival.

This concern has lead to the 1992 Rio Treaty and the Kyoto Protocol of1997. These call for significant decrease in the amount of carbondioxide released to the atmosphere from the burning of fossil fuels bythe industrial world. If these reductions are put into effect, thenserious adverse consequences are expected. The economy of theindustrialized world could be significantly, adversely affected. Thiscould result in a loss of jobs, decreases in the standard of living,reduction in life span and possible political unrest. Moreover, thiswould not be a solution because it does not permit or require a reversalof the currently increasing levels of carbon dioxide in the atmosphere.

Carbon dioxide is released into the atmosphere both by the burning offossil fuels, and by the recycling of plant materials. Carbon dioxide isremoved from the atmosphere by the photosynthesis of plants on land andin the oceans. This removal of carbon dioxide from the atmosphere may bereferred to as a carbon dioxide sink. It is the net flow (releases minussinks) that has caused the increase in atmospheric carbon dioxide levelwhich is of present concern. Without human intervention, the net flow ofcarbon dioxide in and from the atmosphere is roughly zero, with thesources and sinks are in rough balance. When fossil fuels are burned,only about 60 percent of the released carbon dioxide is subsequentlytaken out of the atmosphere by natural sinks. The remaining about 40percent increases the carbon dioxide level of the atmosphere, leading toconcern over climate changes.

The net carbon dioxide released into the atmosphere can be reduced, butnot eliminated, by increasing the efficiency of power-producingequipment and by harnessing wind and solar power. Generally speaking,these approaches are costly and may be reaching their practical limits.We have been increasing the efficiency of heat engines for over 200years, and may be approaching the limits of basic thermodynamics. It isvery costly to harness low intensity power sources such as wind, waves,sunlight and ocean thermal gradients, especially where energyrequirements are large. Moreover, these approaches can only reduce theincrease in carbon dioxide concentration, never eliminate the increase.Therefore, these approaches cannot adequately address the concern overthe increasing carbon dioxide content of the atmosphere.

The technology of carbon dioxide sink enhancement is in its infancy. Thesequestering of carbon dioxide in geological formations is bothbeneficial and inexpensive, if the carbon dioxide is relativelyconcentrated. An example of relatively concentrated carbon dioxide isthe off-gas after removal of methane from natural gas containing carbondioxide. However, there is relatively little carbon dioxide available insuch concentrated form. Most carbon dioxide is available inconcentrations of from about 10 percent to about 25 percent in exhaustgases from the combustion of fossil fuels. It is quite expensive toincrease the concentration of carbon dioxide from about 10 or 25 percentto about 100 percent. The preferable course of action appears to be theuse of sunlight and plants to do the concentrating, and subsequently tosequester the resulting plant material in some manner.

One approach would be to plant trees. However, there is not enough landto plant sufficient trees to zero out the net carbon dioxide production.Even if there were enough land, we would have to find a place to storethe resulting wood after about 50 to about 100 years, such that the woodwould not rot and release carbon dioxide to the atmosphere. Thus, thisapproach would not sequester carbon dioxide for a relatively long periodof time.

The best place to enhance plant growth is in the oceans. Ninety-eightpercent of the surface of the ocean is a barren desert with almost noplant life. About sixty percent of the plant life (phytoplankton) in theoceans of the world arises from about only two percent of the surface ofthe oceans.

SUMMARY OF THE INVENTION

A method of sequestering carbon dioxide comprises the following steps:testing an area of the surface of an ocean for suitability; fertilizinga suitable area of the surface of the ocean to increase plant life andsequester carbon dioxide; and measuring the amount of carbon dioxidethat has been sequestered. The method may include the additional step ofreporting the amount of carbon dioxide that has been sequestered. Anarea of the surface of an ocean is suitable if both at least onenutrient is missing to a significant extent, and the water is deep. Anutrient is missing to a significant extent, if the metabolism of carbondioxide is reduced to a significant extent by the level of the nutrientin the water. An appropriate amount of a missing nutrient is an amountto raise the concentration of the nutrient at the ocean surface so thatthe metabolism of carbon dioxide is no longer reduced to a significantextent by the concentration of the nutrient. The depth of the water ispreferable at least about 5,000 feet (about 1524 meters), morepreferably at least about 10,000 feet (about 3048 meters), and mostpreferably at least about 15,000 feet (about 4572 meters). Thefertilizing creates a new verdant zone, preferably in the ocean surfaceabove very deep water. The testing and reporting may be carried out byany of a number of methods that are known to one of ordinary skill inthe art. The reporting may be carried out in a number of forms.Conventional forms would include printing the report on paper or anothersubstrate, or storing the report in magnetic media or optical media. Thereport may be in a form required by our governmental authority. Suchgovernmental authority may monitor the amount of carbon dioxide that isreleased into the atmosphere by a particular person or company. Theamount of carbon dioxide released may be a debit on the balance sheet ofsuch person or company. The governmental authority may allow credits onsuch balance sheet for the amount of carbon dioxide stated in suchreport as being sequestered.

DETAILED DESCRIPTION OF THE INVENTION

Sequestration of carbon dioxide by fertilizing a suitable area of thesurface of an open ocean has a number of benefits. Substantial amountsof carbon dioxide may be sequestered for substantial periods of time.The present invention may sequester all of the net carbon dioxideproduced by the burning of fossil fuels because about 53 percent of thecarbon taken out of the ocean (and from the atmosphere) by the processof the present invention is expected to be sequestered in the deep oceanfor about 1,000 to about 2,000 years, as has been measured in the deep,tropical Pacific Ocean. The present invention should not be carried outin a shallow bay or lake because this could produce anoxic conditions.

The barren ocean may be made verdant by adding the missing nutrients tothe ocean surface. This occurs naturally in the upwelling off of Peruwhere nutrient-rich bottom water comes to the surface and thephytoplankton bloom.

Whether an area of the surface of an ocean is suitable for sequesteringcarbon dioxide depends on a number of factors. The depth of the oceanshould be sufficient to prevent the significant development of anoxicconditions after fertilization. The depth of the thermocline ispreferably less than the depth of the photic zone, such that thethermocline prevents the fertilizer from reaching a depth below thephotic zone. The photic zone extends from the surface of the ocean to adepth of from about 150 to 300 feet (about 46 to 91 meters), generallyspeaking. The photic zone may best be described functionally. It extendsfrom the surface to a depth where sunlight no longer causes anappreciable amount of photosynthesis. However, if the depth of thethermocline is greater than the depth of the photic zone, then thefertilizer may comprise a float material to prevent the fertilizer fromsinking to a depth below the photic zone. The amount and nature of thefertilizer depends on the nutrients that are missing from the surface ofthe ocean. Preferably, iron is the only nutrient that is missing to asignificant extent from the area of the ocean to be fertilized. Thisallows fertilization with a fertilizer that comprises only iron salts,and preferably iron chelates that prevent the iron from precipitating toany significant extent. The preferred chelates include lignin, andparticularly lignin acid sulfonate. However, other nutrients may bemissing from the surface of the ocean. If nitrogen is missing to asignificant extent, then the fertilizer may comprise at least onenutrient which causes a bloom of at least one microorganism that fixesnitrogen. The microorganism may be from the group consisting of bluegreen algae and phytoplankton. The surface of the ocean may also bemissing phosphate and trace minerals, which may be incorporated into thefertilizer system. If the surface of the ocean is missing both iron andan additional nutrient, then the preferred method may include theseparate application of a plurality of fertilizers. The first fertilizerpreferably includes iron, and more preferably an iron chelate. The othermissing nutrients may be applied in a second fertilizer, or in aplurality of additional fertilizers. It is preferred that eachfertilizer release the corresponding nutrient in a form that does notreact with any iron chelates in the first fertilizer and that does notprecipitate to any substantial extent.

The amount of carbon dioxide that is sequestered by carrying out afertilization according to the present invention depends upon a numberof factors. The composition, amount and rate of distribution of thefertilizer are all factors. The nutrient content of the water of theocean is also a factor, not only at the location of the application ofthe fertilizer, but also all locations to which the fertilized water issubsequently carried by any currents. The temperature and amount ofsunlight are factors. The nature and number of the organisms in thewater that metabolize the fertilizer or that eat the plant materialsproduced, are also factors.

The primary missing nutrient is iron in much of the surface of theoceans. In an experiment, iron salts were added to a portion of thesurface of the barren tropical Pacific ocean. A bloom of phytoplanktonresulted. This plant bloom turned the ocean from deep blue to milkygreen and drew down the carbon dioxide concentration in the fertilizedwater. The phytoplankton increased about 27 times versus background inabout nine days, as a result of fertilization with iron salts during thefirst, fourth and eighth days (days zero, three and seven of theexperiment). This plant bloom occurred in spite of the relatively lowefficiency of the fertilizer that was used (about 95 percent of the ironprecipitated out of the photic zone shortly after application).

A test has been carried out to evaluate the application of fertilizersthat comprise both iron and phosphate. The initial fertilizationproduced a bloom of phytoplankton of about 4.5 to 7 times the initialconcentration of such phytoplankton, in just over one day. Adverseweather and ocean conditions after the first day precluded furthereffective measurements.

A second test has been carried out to evaluate the application of aniron fertilizer. Iron-containing pellets were dispersed over a ninesquare mile patch of open ocean. This resulted in an increase ofphytoplankton concentration of about five times the backgroundconcentration of phytoplankton. The maximum bloom appeared to be about600 pounds of phytoplankton per pound of fertilizer, by extrapolatingover the increasing size of the patch at nearly constant phytoplanktonconcentration.

The measurement of the amount of carbon dioxide that is sequestered bycarrying out the fertilization of the present invention may require thatsome estimates be made. Dissolved inorganic carbon may be removed fromthe water at the surface of the ocean by three mechanisms: (1) some willgo to the bottom of the ocean as sinking organic particles; (2) somewill be dispersed by currents; and (3) some will be degassed to theatmosphere over the ocean. Numerous organisms may metabolize eachnutrient including inorganic nitrogen that is available at the surfaceof the ocean. These organisms may be removed from that area of thesurface of the ocean by two mechanisms: (1) some will go to the bottomof the ocean as sinking organic particles; and (2) some are dispersed bythe current or swimming. None are removed to the air over the ocean. Asthese phytoplankton organisms metabolize each fertilizer, they usuallyuptake both carbon in the form of carbon dioxide and nitrogen in theform of nitrates. Estimates may be made of the amount of organic carbonthat sinks to the bottom of the ocean by assuming that the amount oforganic carbon that sinks to the bottom of the ocean is proportional tothe amount of organic nitrogen that sinks to the bottom of the ocean.The amount of organic nitrogen that sinks to the bottom of the ocean canbe measured from the draw down of inorganic nitrates and thecarbon-nitrogen ratios in the organic materials formed. As the particlesof organic carbon sink below the main thermocline, this organic carbonis effectively sequestered in the deep ocean for periods of timeapproaching the time scale of organic turnover which is from about 100to about 10,000 years.

The present invention allows for the sequestration of substantialamounts of carbon dioxide. Preliminary calculations indicate that foreach year, for each square mile of deep tropical ocean fertilized, about17,000 tons of carbon dioxide containing about 4,600 tons of carbon maybe converted to biomass and sequestered to the ocean floor. After asubstantial period of time such as over the next 1,000 years, most ofthis carbon is expected to be oxidized to carbon dioxide and returned tothe surface of the ocean in the form of super-saturated ocean upwellingsbut a part will remain in the deep ocean in the form of calciumcarbonate and other carbonaceous materials. Therefore, the presentinvention may sequester the 40 percent of the carbon dioxide that theU.S. produces by burning fossil fuels each year and that is not takenout by natural sinks, if this continuous fertilization is carried outover 140,000 square miles of deep barren ocean surface. The estimatedcurrent cost is about $5 per ton of carbon sequestered, when oneconsiders that about 1,000 tons of carbon will be sequestered per ton offertilizer spread over the surface of the deep barren ocean. Thisestimated cost is much lower than the estimated cost of alternativeapproaches primarily because of the use of sunlight to concentrate thecarbon dioxide from the ocean surface and the atmosphere into the formof biomass which is then sequestered naturally over long periods oftime.

There are additional consequences of carrying out the method of thepresent invention. About half the biomass that is created byfertilization according to the present invention will be recycledthrough zooplankton, fish and marine mammals. If there is continuousfertilization according to the present invention of about 140,000 squaremiles of deep barren ocean, then it is estimated that an additional 70million tons of catchable fish per year would be produced, or abouttwo-thirds of the current world fish production. This is based on anestimate of 500 tons of catchable fish per square mile per year undercontinuous fertilization. These estimates may be subject to revisionbecause there are many variables as one moves up the food chain from thephytoplankton. These variables are not particularly well understood oreasy to control. However, it is known that where this fertilizationoccurs naturally, such as off of Peru, the ocean is able to takeadvantage of the available food and produce a bloom of fish. The amountof catchable fish per year per square mile of barren ocean that isfertilized, may be increased by seeding the ocean with filter-feederfish. The introduction of these fish will increase the fraction ofbiological carbon that is recycled to the atmosphere as carbon dioxide,and will decrease the fraction that is sequestered to the ocean depths.Therefore, carbon dioxide sequestration is preferably carried out withfertilization pulses of less than thirty days in a particular area, tolimit the zooplankton and fish growth. The use of fertilization pulsescan increase sequestration of carbon dioxide from as little as tenpercent of organic carbon formed to as much as eighty percent organiccarbon formed. The length of such a fertilization pulse is morepreferably less than about twenty days in a particular area. The timeperiod between fertilization pulses in a particular area is preferablyin excess of about thirty days, and more preferably in excess of aboutforty-five days.

The environmental effects of carrying out the method of the presentinvention are expected to be benign, because the same fertilization hasbeen going on naturally in upwellings for millions of years. The maineffect of carrying out the method of the present invention is expectedto be substantial increases in the food supplies of, and therefore thepopulation of fish, porpoises and whales in the newly created verdantecosystems. Preferably, the fertilization according to the presentinvention will not take place near living coral reefs or in shallowwater, so as to avoid any adverse effect thereon. In any event, theenvironmental effects at the ocean surface of carrying out the presentinvention will be short term, vanishing within about one month from thecessation of fertilization. If at some time in the future it is decidedto carry out such fertilization on a large scale as part of a method ofocean farming, then the carbon dioxide content of the atmosphere mayindeed be significantly reduced and, therefore, the possibleenvironmental effects of such large scale ocean farming should becarefully monitored as large scale ocean farming is implemented.

The ocean fertilization of about 140,000 square miles (about 370,000square kilometers) at a rate of removing about 2 billion tons (about 1.8billion metric tons) of carbon dioxide (CO₂) would initially requireabout 700,000 tons (about 644,000 metric tons) per year of fertilizerand would sequester the net annual carbon dioxide production of theUnited States from burning fossil fuels. This is about 2,000 tons (about1,800 metric tons) per day for 350 days per year. If the fertilizerapplied to the ocean costs about $5000 per ton (about 0.9 metric ton),then the cost is about $3.5 billion per year. This cost includes thecost of monitoring, testing and reporting, so as to optimize the methodof sequestration, including the optimization of the composition of thefertilizer, the application rate and the location of application.

Thus, the present method allows for variation, including variation inthe composition of the fertilizer, as well as the location and nature ofthe application of fertilizer, depending on a number of factors.

Methods of increasing seafood production in the ocean are disclosed byU.S. Pat. Nos. 5,433,173 and 5,535,701, and pending application Ser. No.08/950,418, which are hereby incorporated by reference.

Variations of the invention may be envisioned by those skilled in theart and the invention is to be limited solely by the claims appendedhereto.

I claim:
 1. A method of sequestering carbon dioxide in a deep open ocean comprising the following steps:(1) testing an area of the surface of a deep open ocean, in order to confirm that at least a first nutrient is missing to a significant extent from said area, and to indentify said first missing nutrient, and (2) applying to said area a first fertilizer which comprises said first missing nutrient, to fertilize said area with an appropriate amount of said first missing nutrient whereby carbon dioxide is sequestered, (3) limiting zooplankton and fish growth in said area by applying said first fertilizer in pulses; and (4) measuring the amount of sequestered carbon dioxide that results from said fertilization of said area.
 2. The method of claim 1, wherein said first fertilizer comprises an iron chelate, and said chelate comprises lignin acid sulfonate.
 3. The method of claim 1, wherein said testing further comprises testing said area in order to confirm that at least a second nutrient is missing to a significant extent from said area, and to identify said second missing nutrient, and further comprising the applying of a second fertilizer which comprises said second missing nutrient in a form that does not precipitate to any substantial extent, and said second fertilizer does not comprise iron.
 4. The method of claim 1, wherein substantially all of said first fertilizer remains in the photic zone and available to the phytoplankton in said ocean.
 5. The method of claim 1, wherein said testing further comprises a determination that in said area the depth of the thermocline is less than the depth of the photic zone.
 6. The method of claim 1, wherein said testing further comprises testing said area to determine the depth of said open ocean, and wherein said depth is in excess of about 5,000 feet.
 7. The method of claim 1, further comprising the following step:(5) reporting the amount of sequestered carbon dioxide that results from said fertilization of said area.
 8. The method of claim 7, wherein said testing further comprises testing said area in order to confirm that at least a second nutrient is missing to a significant extent from said area, and to identify said second missing nutrient, and further comprising the applying of a second fertilizer which comprises said second missing nutrient in a form that does not precipitate to any substantial extent, and said second fertilizer does not comprise iron.
 9. The method of claim 7, wherein said testing further comprises testing said area to determine the depth of said open ocean, and wherein said depth is in excess of about 5,000 feet.
 10. The method of claim 7, wherein substantially all of said first fertilizer remains in the photic zone and available to the phytoplankton in said ocean.
 11. The method of claim 7, wherein said testing further comprises a determination that in said area the depth of the thermocline is less than the depth of the photic zone.
 12. The method of claim 7, wherein said reporting further comprises delivering a report of the amount of sequestered carbon dioxide, wherein said report is fixed in a tangible form selected from printing on a substrate, or data stored in magnetic or optical media.
 13. The method of claim 7, wherein said pulses in said area are separated by a time period in excess of about thirty days.
 14. The method of claim 13, wherein said first fertilizer comprises an iron chelate, and wherein said chelate comprises lignin acid sulfonate.
 15. A method of sequestering carbon dioxide in a deep open ocean comprising the following steps:applying a first fertilizer to an area of the surface of a deep open ocean; and limiting zooplankton and fish growth in said area by applying said first fertilizer in pulses.
 16. The method of claim 15 further comprising the step of providing a statement of the amount of carbon dioxide sequestered.
 17. The method of claim 16, wherein said report is fixed in a tangible form selected from printing on a substrate, or data stored in magnetic or optical media.
 18. The method of claim 16, further comprising a statement that describes an area of the surface of said ocean, where said method was carried out.
 19. The method of claim 15, wherein said pulses in said area are separated by a time period in excess of about thirty days. 